Heating apparatus

ABSTRACT

An apparatus for heating of oil has an elongated burner tube provided with an inlet end for the admission of combustible fuel in direction longitudinally of the tube, and an outlet end for the combustion gases. An inner channel concentrically surrounds the burner tube and defines at least one helical path encircling the same and extending between the ends thereof. An outer channel system concentrically surrounds the inner channel system and defines at least one additional helical path which encircles the inner system and also extends between the two ends. An inlet for oil to be heated communicates with the outer channel system adjacent the inlet end and an outlet for the oil communicates with the inner system adjacent the inlet also so that oil circulates first through the outer channel system and then through the inner channel system. A passage connects the outer system with the inner system adjacent the outlet end of the burner tube to make such circulation possible. A plurality of straight tubes surround the burner tube peripherally and traverse the additional helical path between the inlet and outlet end within the confines of the outer channel system. Guide means guides combustion gases from the outlet end of the burner tube into the conduits.

United States Patent 72] Inventor Paul Luude Hededam Frederikssun'd, Denmark [21] Appl. No. 72,774 [22] Filed Sept. 16, 1970 [45] Patented Jan. 4, 1972 [7 Assignee Fql s b l S!a!in! !r 9;

Frederikssund, Denmark [32] Priority Nov. 24, 1969 Germany [31] P19 58 884.2

[54] HEATING APPARATUS 10 Claims, 2 Drawing Figs.

[52] US. Cl

[56] Refenences Cited UNITED STATES PATENTS 2,656,821 10/1953 Ray 2,924,203 2/1960 Loebel Primary Examiner-Kenneth W. Sprague Attorney-Michael S. Striker ABSTRACT: An apparatus for heating of oil has an elongated burner tube provided with an inlet end for the admission of combustible fuel in direction longitudinally of the tube, and an outlet end for the combustion gases. An inner channel concentrically surrounds the burner tube and defines at least one helical path encircling the same and extending between the ends thereof. An outer channel system concentrically surrounds the inner channel system and defines at least one additional helical path which encircles the inner system and also extends between the two ends. An inlet for oil to be heated communicates with the outer channel system adjacent the inlet end and an outlet for the oil communicates with the inner system adjacent the inlet also so that oil circulates first through the outer channel system and then through the inner channel system. A passage connects the outer system with the inner system adjacent the outlet end of the burner tube to make such circulation possible. A plurality of straight tubes surround the burner tube peripherally and traverse the additional helical path between the inlet and outlet end within the confines of the outer channel system. Guide means guides combustion gases from the outlet end of the burner tube into the conduits.

HEATING APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to a heating apparatus, and more particularly to an apparatus for heating oil.

In many applications it is necessary to heat certain fluids, and particularly in applications where oil must be heated for various reasons. For affording such heating apparatus is already known wherein a boiler is provided with a burner tube and wherein the combustion gases from the burner tube flow through gas conduits whereas the oil to be heated flows over and around these gas conduits in concurrent flow with the combustion gases. All of the oil to be heated as well as of the combustion gases is in direction opposite to the direction in which fuel fluid for operating the burner tube is introduced into the latter.

The problem with this known apparatus is the fact that although it affords the desired heating of the oil, it also provides a significant danger that the oil being heated might undergo so-called cracking, that is pyrolysis, where the oil becomes converted into a more volatile oil by cracking of its larger molecules into smaller ones. Although cracking or pyrolysis is of course an accepted approach for the treatment of mineral oils where they are to be converted into more volatile oils suitable for use in internal combustion engines, this decomposition is evidently undesired when the problem at hand involves only the heating of the oil but not its conversion into a more volatile oil. This cracking" takes place, generally speaking, at temperatures in excess of 350 C. and the known apparatus mentioned above has the inherent problem that it cannot reliably prevent such an occurrence. Furthermore, its effectiveness is not as good as is desirable.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to avoid the disadvantages of the prior art.

More particularly it is an object of the present invention to provide an improved heating apparatus for the heating of oil which has a higher degree of efficiency than what is known from the prior art.

An additional object of the invention is to provide such a heating apparatus which avoids the danger of subjecting the oil to be heated to pyrolysis.

A concomitant object of the invention is to provide such an apparatus wherein the flow speed of the oil to be heated is so controlled that precisely in the regions where the oil comes in heat-exchanging contact with the hottest heat-exchanging surfaces, it moves at highest flow speed and accordingly is in shorter contact with these heat-exchange surfaces with concomitant reduction of the danger of pyrolysis.

In pursuance of the above objects, and others which will become apparent hereafter, an apparatus according to the present invention may comprise, according to one embodiment and briefly stated, wall means defining an elongated burner tube having an inlet end for admission of combustible fluid and in direction longitudinally of the tube, and an outlet end for combustion gases. An inner channel system concentrically surrounds the burner tube and defines at least one helical path encircling the same and extending from one towards the other of the ends of the burner tube. An outer channel system in turn concentrically surrounds the inner channel system and defines at least one additional helical path encircling the inner system and also extending from one towards the other of the ends. lnlet means for oil to be heated communicates with the outer system in the region of the inlet end of the burner tube, and outlet means for heated oil communicates with the inner system also in the region of the inlet end of the burner tube. Passage means connects the inner system with the outer system in the region of the outlet end of the burner tube. A plurality of at least substantially straight conduits surround the burner tube peripherally-that is are circumferentially distributed with reference to the burner tube-and traverse the aforementioned additional helical path from the outlet end towards the inlet end within the confines of the outer channel system. Finally, guide means is provided which guides the combustion gases at the outlet end of the burner tube into the conduits for movement therein towards the inlet end. In an apparatus so constructed the oil is admitted at the inlet means and passes first through the outer channel system towards the outlet end where it enters through the passage means into the inner channel system to reverse its direction of flow and pass towards the inlet end of the burner tube to leave the inner channel system through the outlet means provided for this purpose. In so doing the oil exchanges heat with the combustion gases while it flows through the outer system counter to the flow of the combustion gases, and thereupon exchanges heat with the wall means surrounding the burner tube while it flows through the inner system in direction counter to the incoming fuel fluid which is admitted into and burned in the burner tube.

An apparatus constructed in the above exemplary manner has the advantages which have been outlined before and avoids the disadvantages known from the prior art. Furthermore, it has the additional advantage that an optimum heatexchange surface temperature is achieved for heating the flowing oil, with a concomitant reduction of the pressure loss in the channel systems. By providing this apparatus with suitably arranged thermoelements which are located in the flow path of the oil at points where overheating of the oil is to be feared or expected, and by connecting these thermoelements (sensors of'known construction) with the controls for the admission and/or ignition of fuel fluid admitted into the inlet end of the burner tube, the danger of cracking or subjecting the oil to pyrolysis is avoided. When a critical temperature is reached at these various points, or at any one of them, the sensors deactivate the admission means and/or ignition means so that-although the heated oil continues to circulate in its paththe temperature in the burner tube drops with a concomitant decrease in the heat transmitted to the oil; this results in affording the apparatus the maximum possible protection against danger from undesired pyrolysis.

According to a further embodiment of the invention the cross-sectional area of the inner channel system is advantageously substantially smaller than the cross-sectional area of the outer channel system. This results in a substantially increased flow speed of the oil to be heated at precisely those locations where it comes in heat-exchanging contact with the wall means bounding the burner tube and where the maximum heat exchange takes place. Thus, although the oil will receive a substantial amount of heat energy by contact with the wall means, the high flow speed of the oil precludes the danger of pyrolysis resulting from such contact.

I have further found that the spaces between consecutive convolutions of the divider walls which define in the inner channel system and in the outer channel system the respective helical paths, that is the pitch of the consecutive convolutions of these divider walls, may be varied and selected with reference to the cross-sectional areas of the channel system and with further reference to the temperatures which are to be expected at the various heat-exchange surface portions, in such a manner that optimum heat exchange takes place all along the respective helical paths. In other words, two parameters have been identified which are of importance for the flow speed of the oil to be heated, namely the cross-sectional areas of the inner and outer channel systems and the pitch of consecutive convolutions of the divider walls defining the helical paths in these channel systems. The cross-sectional areas of the channel systems in effect provide a preliminary determination in the sense that the cross-sectional of the inner channel system is smaller than that of the outer channel systems with a concomitant increase in the rate of flow of oil through the inner channel system as it enters the latter from the outer channel system. Specific adjustments with respect to the flow speed at particular portions of the respective paths can be provided by suitably selecting the pitch of the consecutive convolutions of the helical divider walls in the respective area. In other words, the convolutions can be closer together for instance in the region of the center-intermediate the opposite ends-of the burner tube in the inner channel system, because in this region the highest temperature developed so that a more rapid flow of the oil in this region is desirable.

It will be appreciated that simple calculations and experimentation well within the purview of those having ordinary skill in the art will suffice to determine, on the basis of what has just been set forth above, the necessary dimensioning of the cross-sectional areas of the inner and outer channel systems, and of the spaces or pitch of consecutive convolutions of the divider walls.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section through an apparatus according to the present invention; and

FIG. 2 is a transverse section through the apparatus shown in FIG. 1, taken on the line 11- of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail it will be seen that reference numeral 1 identifies the interior of a burner tube which is bounded and defined by wall means 4. The cross-sectional configuration of the burner tube is shown as circular, but need not necessarily be of such geometry. The outside of the wall means 4 is surrounded by an inner channel system 2 concentric with the burner tube 1, and concentric with the channel system 2 is an outer channel system 3. FIG. 2 shows particularly clearly that the cross-sectional area of the inner channel system is substantially smaller than the cross-sectional area of the outer channel system. The inlet end of the burner tube is the one shown in FIG. 1 at the left-hand end of the burner tube 1, and the outlet end is the one shown in FIG. 1 at the right-hand end. At the left-hand end, that is the inlet end, a combustible fuel fluidusually oil-is admitted by suitable means-which are known per se and thus not disclosed in detail-in the direction of the broken line arrow 7. This fuel fluid becomes combusted in the burner tube 1 and leaves the latter at the right-hand or outlet end (see FIG. 1) in form of combustion gases, as again shown by the broken line arrows 7 which, however, at the right-hand end of the burner tube 1 in FIG. I are shown as being curved.

An inner divider wall 6 surrounds the axis of the burner tube 1 within the inner channel system 2, that is it is helically convoluted about the wall means 4 between the latter and the outer wall 2a of the inner channel system 2. A similar divider wall 5 is equally helically convoluted in the space of the outer channel system 3, between the wall 20 and the outer wall 3a of the outer channel system 3. Thus, the wall 5 defines a helical path extending between the opposite ends of the burner tube 1, and similarly the wall 6 defines another helical path, also extending between the opposite ends of the burner tube 1.

The path defined within the outer channel system 3 by the helical divider wall 5 is traversed by circumferentially distributed straight conduits 11 located within the outer channel system 3 and extending from the outlet end to the inlet end, or at least towards the inlet end, of the burner tube 1 as seen in FIG. 1. The arrangement of the conduits 11 is clearly shown in FIG. 2 in particular. A smoke chamber 15 is provided at the outlet end of the burner tube 1 and it will be seen that the curved broken line arrows 7 indicate how the combustion gases entering the smoke chamber 15 are deflected and are caused to enter the open ends of the conduits 11 through which they then flow in the direction towards the inlet end of the burner tube 1 to leave the conduits 11 via an annular colle'cting chamber or conduit 16 as indicated at the upper lefthand corner of FIG. I, again by the arrows 7. How the combustion gases are subsequently led away is of no interest and is entirely conventional.

A passage such as an opening or the like is identified with reference numeral 17 and connects the outer channel system 3 with the inner channel system 2 in the region of the outlet end of the burner tube 1. As already pointed out, the crosssectional area of the inner channel system 2 is substantially smaller than that of the outer channel system 3, as is evident from a comparison of the radial thickness d of the inner channel system 2 and the radial thickness D of the outer channel system 3, both of which are shown in FIG. 2.

The oil to be heated is admitted into the outer channel system 3 through the inlet means 9, as indicated by the fullline arrow 8, and thereupon traverses the helical path in the outer channel system 3 in the direction towards the aperture 17 as again illustrated by the full-line arrows 8 which are inclined to show the helical path traversed by the oil. In so doing, the oil contacts the conduits 11 around which it flows, and of course exchanges heat with the same. The different pitch of the arrows 8 in the outer channel system 3 (see FIG. 1) is intended to indicate that the pitch of the convolutions of the wall 5 increases in the direction towards the aperture 17 so that the flow speed of the oil also increases as it continues to pass towards the aperture '17. This is done because as the oil approaches the outlet end of the burner tube 1, heat exchange between the oil and the conduits 11 will increase because the combustion gases are of course hotter as they enter the conduits 11 in the region of the outlet end than they are in the region of the inlet end where the oil is first admitted.

The channel systems 2 and 3 are closed off from the chamber 15 by a wall 4a so that the oil, on reaching this wall 4a, is forced to enter through the aperture 17 into the inner channel system 2. Here it comes into direct heat-exchanging contact with the wall means 4 bounding the burner tube 1 and continues to circulate in the inner helical path but now its direction is reversed and it moves towards the inlet end of the burner tube 1, that is towards the left in FIG. 1. Thus, while the oil in the outer channel system 3 was flowing counter to the combustion gases in the conduits 11, in the inner channel system 2 the oil flows counter to the incoming fuel fluid which is admitted at the inlet end (left-hand end of FIG. 1) of the burner tube for flowing in the direction towards the right-hand end. Because of the smaller cross-sectional area of the inner channel system 2 as compared with the outer channel system 3, the oil flows at greater speed through the inner channel system 2 and is allowed to leave the latter at the outlet means 10 which communicates with the inner channel system 2 in the region of the inlet end of the burner tube 1. The distances between consecutive convolutions of the divider wall 6 in the inner channel system 2 are so selected that at no point along the inner channel system 2 is it possible for the oil to become heated to such an extent that pyrolysis would take place. Wherever necessary in the inner channel system 2and if it is considered desirable or necessary this can also be done in the outer channel system 3thermoelements such as known sensors are arranged in the path of the oil and are coupled in a manner which is entirely conventional and forms no part of the present invention, with the controls for admission and/or ignition of fuel fluid into the interior of the burner tube 1, so that these controls terminate admission and/or ignition of fuel fluid when the thermosensors detect and report temperatures in excess of those still permissible.

The exterior of the apparatus is surrounded by an insulating 12 in known manner, and suitable material is well known for such insulating layer and forms no part of the present invention. A door or cover 13 is provided in the region of the outlet end of the burner tube 1, as shown in FIG. I, which can be opened to permit access for inspection, work or cleaning purposes. Thus, more than one door can be provided or another suitable arrangement can be made for affording access, but

the purpose is to afford inspection of all parts in the interior, repair of replacement if and when necessary, and access for cleaning purposes. Because the interior of the apparatus is thus readily accessible any repairs or replacements can be made quickly and downtime for the apparatus as a result of such repairs of replacements is significantly reduced. Furthermore, because the apparatus can be readily cleaned due to such accessibility, the apparatus can be operated with heavy oil, that is it can be used for heating heavy oil.

It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a heating apparatus for the heating of oil, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge, readily adapt it for various applications without omitting features that from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A heating apparatus, particularly for heating of oil, comprising wall means defining an elongated burner tube having an inlet end for admission of combustible fuel fluid in direction longitudinally of said tube, and an outlet end for combustion gases; an inner channel system concentrically surrounding said burner tube and defining at least one helical path encircling the same and extending from one towards the other of said ends; an outer channel system concentrically surrounding said inner channel system and defining at least one additional helical path encircling said inner system and also extending from one towards the other of said ends; inlet means for oil to be heated communicating with said outer system in the region of said inlet end, and outlet means communicating with said inner system also in the region of said inlet end; passage means connecting said outer system with said inner system in the region of said outlet end; a plurality of at least substantially straight conduits surrounding said burner tube peripherally and traversing said additional helical path from said outlet end towards said inlet end within the confines of said outer system; and guide means guiding said combustion gases at said outlet end into said conduits for movement therein towards said inlet end, whereby said oil exchanges heat with said combustion gases while flowing through said outer system counter to said combustion gases, and exchanges heat with said wall means while flowing through said inner system counter to said fuel fluid.

2. An apparatus as defined in claim 1, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system.

3. An apparatus as defined in claim 1, said inner system comprising an inner wall surrounding said wall means with inner clearance, and at least one inner divider wall provided in said clearance and helically encircling said burner tube within said inner clearance; and said outer system comprising an outer wall surrounding said inner wall with outer clearance, and at least one outer divider wall provided in said clearance and helically encircling said burner tube within said outer clearance.

4. An apparatus as defined in claim 3, said outer divider wall comprising a plurality of helical convolutions having a pitch which changes in direction towards said outlet end in a sense effecting an increase in the rate of flow of oil passing through said outer system in direction from said inlet means towards said passage means.

5. An apparatus as defined in claim 1, said guide means defining a combustion gas-collecting chamber receiving combustion gases from said outlet end of said burner tube, and said conduits communicating with said chamber for receiving combustion gases from the same.

6. An apparatus as defined in claim 4, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system.

7. An apparatus as defined in claim 3, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system; and wherein said inner and outer divider walls each comprise a plurality of hellcal convolutions with the pitch of at least some convolutions being different from the pitch of other convolutions in dependence upon the oil flow speed and degree of heat exchange desired to be obtained in the region of the respective convolutions.

8. An apparatus as defined in claim 7, wherein the pitch of the convolutions of said inner divider wall is steeper in the region intermediate said inlet and outlet ends than in the region of said inlet and outlet ends, respectively.

9. An apparatus as defined in claim 5, said guide means comprising a peripheral wall portion bounding said chamber and having an opening for access and cleanout purposes, and a cover portion for removably covering said opening.

10. An apparatus as defined in claim 1, and further comprising discharge means communicating with said conduits in the region of said inlet end for discharging said combustion gases from said conduit means. 

1. A heating apparatus, particularly for heating of oil, comprising wall means defining an elongated burner tube having an inlet end for admission of combustible fuel fluid in direction longitudinally of said tube, and an outlet end for combustion gases; an inner channel system concentrically surrounding said burner tube and defining at least one helical path encircling the same and extending from one towards the other of said ends; an outer channel system concentrically surrounding said inner channel system and defining at least one additional helical path encircling said inner system and also extending from one towards the other of said ends; inlet means for oil to be heated communicating with said outer system in the region of said inlet end, and outlet means communicating with said inner system also in the region of said inlet end; passage means connecting said outer system with said inner system in the region of said outlet end; a plurality of at least substantially straight conduits surrounding said burner tube peripherally and traversing said additional helical path from said outlet end towards said inlet end within the confines of said outer system; and guide means guiding said combustion gases at said outlet end into said conduits for movement therein towards said inlet end, whereby said oil exchanges heat with said combustion gases while flowing through said outer system counter to said combustion gases, and exchanges heat with said wall means while flowing through said inner system counter to said fuel fluid.
 2. An apparatus as defined in claim 1, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system.
 3. An apparatus as defined in claim 1, said inner system comprising an inner wall surrounding said wall means with inner clearance, and at least one inner divider wall provided in said clearance and helically encircling said burner tube within said inner clearance; and said outer system comprising an outer wall surrounding said inner wall with outer clearance, and at least one outer divider wall provided in said clearance and helically encircling said burner tube within said outer clearance.
 4. An apparatus as defined in claim 3, said outer divider wall comprising a plurality of helical convolutions having a pitch which changes in direction towards said outlet end in a sense effecting an increase in the rate of flow of oil passing through said outer system in direction from said inlet means towards said passage means.
 5. An apparatus as defined in claim 1, said guide means defining a combustion gas-collecting chamber receiving combustion gases from said outlet end of said burner tube, and said conduits communicating with said chamber for receiving combustion gases from the same.
 6. An apparatus as defined in claim 4, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system.
 7. An apparatus as defined in claim 3, said inner system having a cross-sectional area which is substantially smaller than the cross-sectional area of said outer system; and wherein said inner and outer divider walls each comprise a plurality of helical convolutions with the pitch of at least some convolutions being different from the pitch of other convolutions in dependence upon the oil flow speed and degree of heat exchange desired to be obtained in the region of the respective convolutions.
 8. An apparatus as defined in claim 7, wherein the pitch of the convolutions of said inner divider wall is steeper in the region intermediate said inlet and outlet ends than in the region of said inlet and outLet ends, respectively.
 9. An apparatus as defined in claim 5, said guide means comprising a peripheral wall portion bounding said chamber and having an opening for access and cleanout purposes, and a cover portion for removably covering said opening.
 10. An apparatus as defined in claim 1, and further comprising discharge means communicating with said conduits in the region of said inlet end for discharging said combustion gases from said conduit means. 